Oxidation-resistant lubricating composition



United States Patent 3,151,075 OXIDATION-RESISTANT LUBRICATING COMPGSITION Thomas A. Butler, Cleveland, Ohio, assignor to The Lubrizol Corporation, iekliife, Shin, a corporation of Ohio No Drawing. Filed Mar. 3, 1961, Ser. No. 3,04-6 14 Claims. (Cl. 25232.7)

This invention relates to lubricating compositions and in a more particular sense to lubricating compositions having improved oxidationand corrosion-inhibiting properties. In a still more particular sense this invention relates to lubricating compositions characterized by a reduced tendency to cause corrosion of the metal surfaces which they lubricate.

Lubricating oils are susceptible to oxidation upon prolonged exposure to air at elevated temperatures. Oxidation results in the formation of organic acids, alcohols, ketones, aldehydes, etc. These products, especially the organic acids, are corrosive to metal and this corrosive action is a principal cause of excessive wear of the metal parts coming into contact with the oils. It is thus a common practice to incorporate into mineral lubricating oils chemical additives which are capable of inhibiting oxidation of the oil. The effective oxidation inhibiting addtives include the phosphorothioates such as metal phosphorodithioates and adducts of metal phosphorodithioates with epoxides.

Unfortunately, however, the phosphorothioateshave a 9 tendency to react with the metal surface with which they come into contact at high temperatures and pressures. This reaction usually manifests itself in thedeposition on the metal surface of a coating of the reaction product. Such coating has the semblance of a black stain and the phenomenon of its formation is thus commonly referred to as black staining of the metal surface. The coating is only temporary. It eventually becomes loosened from the surface and the freshly exposed metal again becomes susceptible to chemical attack by phosphorothioates or oil oxidation products. The ultimate result is depreciation of the metal surface. In this respect, the formation of black stain represents a form of corrosive Wear of the metal surface and is objectionable.

The formation of black stain is objectionable also because it impairs the frictional characteristics of the metal surface and alters the clearance between the relatively moving metal parts. Hence, phosphorothioates have not been widely used heretofore in lubricating compositions intended for lubricating metal parts which depend for their successful operation upon exacting frictional characteristics and precise clearance.

Furthermore it is known that despite their 'eflicacy' un- It is further an object of this invention to provide a method for enhancing the oxidation stability oflubricat ing compositions containing phosphorothioates.

These and other objects are attained in accordance with this invention by providing a lnbricating composi- 7 metal neutralizing agent such as zinc oxide or barium 3,151,075 Patented Sept. 29, 1964 "ice tion comprising a major proportion of a lubricating oil, from about 0.001% to 2% by'weight of; phosphorus as a phosphorothioate additive selected from the group consisting of oil-soluble Group II metal phosphorodithioates and the adducts of said metal phosphorodithioates with up to about 0.75 mole of an epoxide, and a small amount,

and comprise preferably the salts of calcium, barium, strontium, zinc, and cadmium With phosphorodithioic acids having the formula Rio\ %s P 1220 \SH wherein R and R are substantially hydrocarbon radicals 'such as alkyl, alkaryl, arylalkyl, and cycloalkyl radicals and contain a total of at least about 7.6 aliphatic carbon atoms per atom of phosphorus. They include,-for example, the Group II metal phosphorodithioates described in U.S. Patents 2,680,123; 2,689,220; 2,364,283; 2,364,284; 2,261,047; 2,329,436; 2,344,393; 2,368,800; 2,386,207; 2,388,199; Re. 22,830; Re. 22,829; and 2,838,535. The

zinc and barium phosphorodithioates are particularly effective as additives in lubricating compositions and are therefore preferred for the use herein.

The'above limit with respect to-the minimum number of aliphatic carbon atoms in R and R radicals per phosphorus atom is based upon the oil solubility of the metal phosphorodithioates, i.e., those prepared from phosphorodithioic acids in which R, and R containa total of less than about 7.6 aliphatic carbon atoms are not sufliciently soluble in lubricating oils'to be useful as additives. 'For reasons of economy the substantially hydrocarbon radicals in the phosphorodithioic acids are preferably low or medium molecular weight alkyl radicals and lower alkylphenyl radicals, i.e., those having from '3 to about'30 carbon atoms in the alkyl radical. Illustrative alkyl radicals include methyl, ethyl, isopropyl, isobutyl, n-butyl, secbutyl, n-pentyl, neopentyl, 3-rnethyl-butyl, n-heptyl, methyl-isobutyl, Z-ethyl-hexyl, di-iso-butyl, iso-octyl, and 'deceicosyl, butyl-naphthyl, hexylnaphthyl, cyclohexylphenyl,

and naphthenyh likewise are useful. Many substituted hydrocarbon radicals such as bromoalkyl, chloroalkyl, dichloropheny'l, and chloroalkyl-phenyl radicals may also be used. 7 The availability of thephosphorodithioic acids'frorn which the metal salts are prepared is well' known. They are prepared, forexam'pl by the reaction of phosphorus pentasnlfide with an-alcoholor a phenol. The reaction involves 4 moles of the alcohol or phenol per mole of phosphorus'pentasulflde and may be carried out within '.the temperature rangefrom about 50 C. to about 200 C., preferably from about C. to about 120 C. 'Thus, the preparation'of di-n-hexylphosphorodithioic acid in volves the reaction of phosphorus pentasulfide with 4 moles-of n hexyl alcohol at about C. for about'2 hours. Hydrogen sulfide is liberated and the residue is the defined acid. The preparation of the metal salt of thisacid may be effected by reaction of theacid with a oxide. Simply mixing and heating these reactants is willcient to cause the neutralization to take place and the resulting product is sufficiently pure for the purpose of this invention.

Especially useful metal phosphorodithioates can be prepared from phosphorodithioic acids which in turn are prepared by the reaction of phosphorus pentasulfide with mixtures of alcohols. The use of mixtures of alcohols enables the utilization of cheaper alcohols which by themselves do not yield oil-soluble phosphorodithioate acids salts. Thus, a mixture of isopropyl and hexyl alcohols can be used to produce a very effective oil-soluble metal phosphorodithioate. For the same reason mixtures of simple acids i.e., acids prepared from a single alcohol, can be reacted with the metal neutralizing agent to produce less expensive oil-soluble metal salts.

Another class of the phosphorothioate additives contemplated for use in the lubricating compositions of this invention comprises the adducts of the metal phosphorodithioates described above with up to about 0.75 mole of an epoxide. The metal phosphorodithioates useful in preparing such adducts are for the most part the zinc phosphorodithioates. The epoxides may be alkylene oxides or arylalkylene oxides. The arylalkylene oxides are exemplified by styrene oxide, p-ethylstyrene oxide, alphamethylstyrene oxide, B-beta-naphthyl-1,3-butylene oxide, m-dodecylstyrene oxide, and p-chlorostyrene oxide. The alkylene oxides include principally the lower alkylene oxides in which the alkylene radical contains 6 or less carbon atoms. Examples of such lower alkylene oxides are ethylene oxide, propylene oxide, l,2-butene oxide, tri- .rnethylene oxide, tetramethylene oxide, butadiene monoepoxide, 1,2-hexene oxide, and propylene epichlorohydrin. Other epoxides useful herein include, for example, butyl 9,10-epxystearate, epoxidized soya bean oil, epoxidized tung oil, and epoxidized copolymer of styrene with butadiene.

The adduct may be obtained by simply mixing the phos phorodithioate and the epoxide. The reaction is usually exothermic and may be carried out Within wide temperature limits from about 0 C. to about 300 C. Because the reaction is exothermic it is best carried out by adding one reactant, usually the epoxide, in small increments to the other reactant in order to obtain convenient control of the temperature of the reaction. The reaction may be carried out in a solvent such as benzene, mineral oil, naphtha, or n-hexane.

The chemical structure of the adduct is not known. For the purpose of this invention adducts obtained by the reaction of one mole of the phosphorodithioate with from about 0.25 mole to about 0.5 mole of a lower alkylene oxide, particularly ethylene oxide and propylene oxide, have been found to be especially useful and therefore are preferred.

The preparation of such adducts is more specifically illustrated by the following example: To 394 parts (by weight) of zinc dioctylphosphorodithioate having a phosphorus content of 7% there is added at 75 85 C., 13 parts of propylene oxide (0.5 mole per mole of the zinc phosphorodithioate) throughout a period of 20 minutes. The mixture is heated at 8285 C. for 1 hour and filtered. The filtrate (399 parts) is found to contain 6.7% of phosphorus, 7.4% of zinc, and 4.1% of sulfur.

This invention contemplates also the presence of other additives in combination with the phosphorothioate additive and anthranilic acid in lubricating compositions. Such additives include, for example, detergents of both ash-containing and ashless types, viscosity index improving agents, pour point depressing agents, anti-foam agents, extreme pressure agents, rust inhibiting agents, and supplemental oxidation and corrosion inhibiting agents.

The ash-containing detergents are exemplified by oilso'luble neutral and basic salts of alkali or alkaline earth metals with sulfonic acids, carboxylic acids, or organic phosphorus acids characterized by at least one direct carbon-to-phosphorus linkage such as those prepared by the treatment of an olefin polymer (e.g., polyisobutene having a molecular Weight of 1000) with a phosphorizing agent such as phosphorus trichloride, phosphorus heptasulfide, phosphorus pentasulfide, phosphorus trichloride and sulfur, white phosphorus and a sulfur halide, or phosphorothioic chloride. The most commonly used salts of such acids are thOse of sodium, potassium, lithium, calcium, magnesium, strontium, and barium. The term basic salt is used to designate the metal salts wherein the metal is present in stoichiometrically larger amounts than the organic acid radical. The commonly employed methods for preparing the basic salts involve heating a mineral oil solution of an acid with a stoichiometric excess of a metal neutralizing agent such as the metal oxide, hydroxide, carbonate, bicarbonate, or sulfide at a temperature above 50 C. and filtering the resulting mass. The use of a promoter in the neutralization step to aid the incorporation of a large excess of metal likewise is known. Examples of compounds useful as the promoter include phenolic substances such as phenol, naphthol, alkylphenol, thiophenol, sulfurized alkylphenol, and condensation products of formaldehyde with a phenolic substance; alcohols such as methanol, 2-propanol, octyl alcohol, Cellosolve, carbitol, ethylene glycol, stearyl alcohol, and cyclohexyl alcohol; amines such as aniline, phenylenediamine, phcnothiazine, phenyl-beta-naphthylamine, and dodecylamine. A particularly efiective method for preparing the basic salts comprises mixing an acid with an excess of a basic alkaline earth metal neutralizing agent, a phenolic promoter compound, and a small amount of water and carbonating the mixture at an elevated temperature such as 60200 C.

The ashless detergents are exemplified by the interpolymers of an oil-solubilizing monomer (e.g., decyl methacrylate, vinyl decyl ether, or high molecular weight olefin) with a monomer containing a polar substituent (e.g., amino-alkyl acrylate or poly(oxy-ethylene)-substituted acrylate); the amine salts, amides, and imides of oil-soluble monocarboxylic or dicarboxylic acids such as stearic acid, oleic acid, tall oil acid, and high molecular weight alkyl or alkenyl-substituted succinic acid. An especially useful ashless detergent is an acylated amine prepared by a process which comprises mixing a high molecular weight substantially aliphatic hydrocarbon (having at least about 50 aliphatic carbon atoms)-substituted succinic acid or anhydride with an ethylene amine (e.g., ethylene diamine or tetraethylene pentamine), heating the mixture to effect acylation and removing the water formed thereby. The hydrocarbon radical in the substituted succinic acid or anhydride is most commonly derived from polymers of lower aliphatic olefins such as isobutene, propylene or ethylene. The temperature for effecting the acylation is usually above C., preferably about l50-200 C. The acylated amines and the method for the preparation of the acylated amines are described in greater detail in co-pending application Serial No. 802,667, filed June 3, 1960.

Extreme pressure addition agents are exemplified by chlorinated aliphatic hydrocarbons such as chlorinated wax; organic sulfides and polysulfides such as ben zyl disulfide, bis-(chlorobenzyl) disulfide, dibutyl tetrasulfide, sulfurized sperm oil, sulfurized methyl ester of oleic acid, sulfurized alkylphenol, sulfurized dipentene, and sulfurized terpene; phosphosulfurized hydrocarbons such as the reaction product of a phosphorus sulfide with turpentine or methyl oleate; phosphorus esters includingprincipally dihydrocarbon and trihydrocarbon phosphites such as dibutyl phosphite, diheptyl phosphite, dicyclohexyl phosphite, pentyl phenyl phosphite, dipentyl phenyl phosphite, tridecyl phosphite, distearyl phosphite, dimethyl naphthyl phosphite, oleyl 4-pentylphenyl phosphite, polypropylene (molecular weight 500)substituted phenyl phosphite, diisobutyl substituted phenyl phosphite; metal thiocarbamates such as zinc dioctyl-dithiocarbamate, and barium heptylphenyl dithiocarbamate.

The phosphorothioate additive is usually present in lubricating oils in amounts such as to impart from about 0.001% to about 2% (by weight) of phosphorus to the final lubricating composition. The optimum amounts for a particular application depend to a large measure upon the type of service to which the lubricating composition is to be subjected. Thus, for example, lubricating compositions for use in gasoline internal combustion engines may contain from 0.01% to about 0.5% of phosphorus as the additive whereas lubricating compositions for use in gears and diesel engines may contain as much as 1% or 2% of phosphorus as the additive. On the other hand, lubricating compositions for use in 2-cycle outboard motor engines may contain as little as 0.005% or even less of phosphorus. The amount or" the anthranilic acid to be used in a lubricating composition is related to the amount of the phosphorothioate additive present in such composition. It has been found, however, that an amount within the approximate limit of 0.01% to 1% by weight of anthranilic acid in the final composition is usually sufiicient to improve the oxidation-inhibiting effectiveness and to counteract the corrosive tendency of the phosphorothioate additive. In most instances, from about 0.02% to about 0.2% of anthranilic acid in a lubricating composition has been found to be sufiicient to achieve the desired result.

The lubricating compositions may also contain detergent additives in amounts usually within the range of about 0.1% to about 20% by weight. In some applications such as in lubricating marine diesel engines the lubricating compositions may contain as much as 30% of a detergent additive. They may also contain extreme pressure addition agents, viscosity index improving agents, and pour point depressing agents, each in amounts Within the range from about 0.1% to about A particularly effective combination of additives for use in lubricating composition for internal combustion engines, gears, and power transmitting units comprises from 0.01% to 2% of phosphorus as the phosphorothioate additive of this invention (i.e., a Group II metal phosphorodithioate or an epoxide adduct thereof), from 0.01% to 1% of anthranilic acid, from 0.1% to 20% of a detergent additive of the oil-soluble alkali or alkaline earth metal soap type such as normal or basic alkali or alkaline earth metal salts of sulfonic acids, carboxylic acids, or organic phosphorus acids described herein-above and/or of the ashless type such as the hydrocarbonsubstituted succinic acid-ethylene amine reaction product, and from 0.1% to 20% of an extreme pressure addition agent such as the dihydrocarbon or trihydrocarbon phosphites, sulfurized fatty oils (e.g., sulfurized sperm oil having a sulfur content of 10%), organic sulfides or polysulfides illustrated above.

The following examples are illustrative of the lubricating compositions of this invention (all percentages are by weight):

EXAMPLE 1 EXAMPLE 2 SAE 30 mineral lubricating oil containing 0.05% of anthranilic acid and 0.1% of phosphorus as the barium salt of di-n-nonylphosphorodithioic acid.

EXAMPLE 3 SAE 10W-30 mineral lubricating oil containing 0.07 5

of anthranilic acid and 0.075% of phosphorus as zinc di-n-octyl-phosphorodithioic acid.

6 EXAMPLE 4 SAE 20W-30 mineral lubricating oil containing 0.075% of anthranilic acid and 0.05 of phosphorus as barium di-heptyl-phenylphosphorodithioate.

EXAMPLE7 SAE l0W-3O mineral lubricating oilcontaining-0.01% of anthranilic acid and 0.05 of phosphorus as the zinc salt of a phosphorodithioic acid prepared by the reaction of phosphorus pentasulfide with a mixture of 60% .(mole) of p-butylphenol' and 40% (mole) of n-pentyl alcohol.

EXAMPLE 8 SAE 50 minerallubricati-ng oil containing 0.08% of anthranilic acid'and- 0.1% of phosphorus as the calcium salt of di-hexylphosphorodithioate.

' EXAMPLEQ SAE 10W-30 mineral lubricating oil containing 0.03% ofanthranilic acid, 0.06% of phosphorus as zinc'di-noctylphosphor-odithioate and 1% of-sulfate ash as barium mahogany sulfonate.

EXAMPLE 10 SAE 30 mineral lubricating oil containing 0.05% of anthranilic acid, 0.1% of phosphorus as the zinc salt of a mixture of equimolar amounts of di-isopropylphosphorodithioic acid and di-n-decylphosphorodithioic acid, and 2.5% of sulfate ash as a basic barium detergent prepared by carbonating at 150 C. a mixture comprisingmineral oil, barium di-dodeeylbenzene sul-fonate and 1.5-moles of barium hydroxide in the presence of a small amount of Water and 0.7 mole of octylphenol as the promoter.

EXAMPLE 11 SAE 10W-30 mineral lubricating oilcontaining 0.05

of anthranilic acid, 0.075 of phosphorus as-the adduct obtained by treating z-inc di-n-octylphosphorodithioate with 0.5 mole of propylene oxide at room-temperature, and 5% of'thebarium salt of an acidic composition prepared by' the reaction of 1000 parts-of a polyisobutene having a1'1no'lecu1arweightof 60,000 with -100-parts-of phosphorus pentasulfide at 200 C. and hydrolyzing the product with steam at 150 C.

, EXAMPLE 12 SAE 10 m-inerahlubricat'ing oil containing 0.05%- of anthranilic acid, 0.075 of phosphorus'as' the adduct of zinc di-cyclohexylphosphorodithioate treated with 0.3

mole of ethylene oxide, 2% of a sulfurized sperm'o il having a sulfur contentof'10'%, 3 .5 of a poly-(alkyl methacrylate) viscosity index improver, 0.02% of a poly- (alkyl methacrylate) pour point depressant, 0.003% ofa V poly-(alkyl siloxane) anti-foam agent, and "2% of-an anthranilic acid, 0.075 of phosphorus as the adduct ob-- ashless detergent prepared bythe reaction of triethylene tetramine with a stoichiometrically equivalent amount of apolyisobutene (molecular weight l000)-substituted succinic anhydride under dehydrating conditions.

EXAMPLE 13 p SAE 10 minerallubricating oil containing 0.04%, of

tained by 'heatingfzinc di-nonylphosphorodithioate with 0.25 mole of 1,2-hexene oxide at 120 C., a sulfurized methyl ester of tall oil acid having a sulfur content of 15%, 6% of a polybutene viscosity index irnprover, 0.005% of a poly-(alkyl methacrylate) anti-foam agent, 2% of the ashless detergent described in Example 12, and 0.5% of lard oil.

EXAMPLE 14 SAE 20 mineral lubricating oil containing 0.03% of anthranilic acid, 0.05% of phosphorus as the adduct of zinc di-heptylphosphorodithioate with 0.5 mole of 1,2- butene oxide, 0.5% of di-dodecyl phosphite, 2% of the sulfurized sperm oil having a sulfur content of 9%, a basic calcium detergent prepared by carbonating a mixture comprising mineral oil, calcium mahogany sulfonate and 6 moles of calcium hydroxide in the presence of an equimolar mixture (10% of the mixture) of methyl alcohol and n-butyl alcohol as the promoter at the reflux temperature.

EXAMPLE 15 SAE 10 mineral lubricating oil containing 0.05% of anthranilic acid, 0.07% of phosphorus as zinc di-octylphosphorodithioate, 2% of a barium detergent prepared by neutralizing with barium hydroxide the hydrolyzed reaction product of a polypropylene (molecular weight 2000) with 1 mole of phosphorus pentasulfide and 1 mole of sulfur, 3% of a barium sulfonate detergent prepared by carbonating a mineral oil solution of mahogany acid, and a 500% stoichiometrically excess amount of barium hydroxide in the presence of phenol as the promoter at 180 C., 3% of an ashless detergent prepared by copolymerizing a mixture of 95% (weight) of a decylmethacrylate and (Weight) of diethylaminoethylacrylate.

EXAMPLE 16 SAE 80 mineral lubricating oil containing 0.05% of anthranilic acid, 0.1% of phosphorus as zinc di-n-hexylphosphorodithioate, of a chlorinated parafl'in Wax having a chlorine content of 40%, 2% of di-butyl tetrasulfide, 2% of sulfurized dipentene, 0.2% of oleyl amide, 0.003% of an anti-foam agent, 0.02% of a pour point depressant, and 3% of a viscosity index improver.

EXAMPLE 17 SAE 10 mineral lubricating oil containing 0.03% of anthranilic acid, 0.075% of phosphorus as the adduct of 0.5 mole of propylene oxide with the zinc salt of a phosphorodithioic acid prepared by the reaction of phosphorus pentasulfide with an equimolar mixture of n-butyl alcohol and dodecyl alcohol, 3% of a barium detergent prepared by carbonating a mineral oil solution containing 1 mole of sperm oil, 0.6 mole of octylphenol, 2 moles of barium oxide, and a small amount of water at 150 C.

EXAMPLE 18 SAE 20 mineral lubricating oil containing 0.1% of anthranilic acid and 0.07% of phosphorus as the adduct of zinc di-n-octylphosphorodithioate with 0.25 mole of propylene oxide.

EXAMPLE 19 SAE 30 mineral lubricating oil containing 0.08% of anthranilic acid and 0.1 of phosphorus as the adduct of zinc di-(isobutylphenyl) -phosphorodithioate with 0.4 mole ofepichlorohydrin.

EXAMPLE 20 SAE 50 mineral lubrication oil containing 0.05% of anthranilic acid and 0.15% of phosphorous as the adduct of zinc di-primary-pentylphorodithioate with 0.3 mole of styrene oxide.

EXAMPLE 21 SAE 90 mineral lubricating oil containing 0.12% of anthranilic acid and 0.2% of phosphorus as the adduct of zinc di-dodecylphosphorodithioate with 0.25 mole of 3,4-hexene oxide.

The above lubricants are merely illustrative and the scope of invention includes the use of all of the additives previously illustrated as Well as others Within the broad concept of this invention described herein.

The effectiveness of anthranilic acid in preventing the formation of black stain on metal parts coming into contact with lubricating composition containing the phophorothioate additive is shown by the results (summarized in Table l) of a test in which a 200 cc. sample of a lubricating composition having immersed therein a steel panel (4 x 1% inch, 20 gauge) and a copper panel (4 x 1 /z inch, 18 gauge) is maintained at 175:2" C. for 8 hours. At the end of the test the two metal panels are inspected visually for the presence of black stain. The lubricant used in the test consists of a mineral lubricating oil having a viscosity of 112 SUS (Saybolt Universal seconds) at F. and a viscosity index value of 85 and containing a basic barium detergent having prepared by heating a mixture of 35% (2.3% by volume, prepared by heating a mixture comprising 1000 parts (by weight) of sperm oil, 294 parts of heptylphenol, 2870 parts of mineral oil, 285 parts of water, and 1540 parts of barium oxide to 300 F., carbonating the mixture at 275 F. until it is substantially neutral, and filtering the product), a basic barium sulfonate detergent having a barium sulfate ash content of 38.5% (0.92% by volume, prepared by heating a mixture comprising 805 parts (by weight) of mineral oil, 625 parts of barium mahogany sulfonate, 210 parts of Water, 146 parts of heptylphenol, and 740 parts of barium oxide to 295 F., carbonating the mixture at this temperature until it is substantially neutral, diluting the mixture with 520 parts of mineral oil, and filtering the product), and a polymeric alkyl siloxane antifoam agent (20 parts by million).

The efiectiveness of anthranilic acid in enchancing the oxidation-inhibiting properties of the phosphorothioate additives in lubricating compositions is demonstrated by the results (summarized in Table II) of an Oxidation Test. The test consists of blowing air at a rate of 1.25 cubic feet per hour at 150 C. into 350 grams of a lubricating composition having immersed therein an oxidation catalyst consisting of grams of iron, 128 grams of copper, and 31 grams of lead until sludge is formed (as indicated by the appearance of haze or sediment).

Table 1 Test Result Test Sample (percent by Weight) Black Stain Steel Panel Black Stain Copper Panel Absent. Present.

Absent.

Absent Present Absent Lubricant Lubrieant+0.08% of phosphorus as zinc dioctylphosphorodithioate.

Lubricant+0.08% of phosphorus as zinc dioetylphosphorodithioate+0.1% of anthranilic acid.

Lubricant+0.08% of phosphorus as the adduct of 1 mole of zinc dioctylphosphorodithioate with 0.5 mole of propylene oxide+0.1% of anthranilic acid.

..do Do.

Table II Test. Result (Hours to Sludge Formation) Test Sample (percent by Weight) The lubricating compositions of this invention have been evaluated further by the Powerglide Transmission Lubricant Test. In this test the lubricating composition is used in a 1955 Chevrolet Powerglide transmission operated under the following conditions: transmission sump temperature, 275 F.; transmission speed, 1750- 1800 r.p.m.; governor pressure, 55-70 psi; and main line pressure, 85-95 p.s.i. Air is bubbled through the lubricant at a rate of 0.12 pran per minute throughout the test. The test is concluded shortly after sediment appears in the lubricant. The lubricant then is evaluated in terms of (1) the time required for the first appearance of sediment, (2) the amounts of varnish and sludge formed (rating scale of -50, 0 representing heavy varnish or sludge and 50 representing no varnish or sludge), (3) the appearance of black stain on the metal parts of the transmission, and (4) the weight loss of the thrust Washer due to corrosion. The results of the test are summarized in Table III.

The lubricating compositions of this invention have been evaluated also by another powerglide Transmission Lubricant Test (results summarized in Table IV). This test consists in operating a Powerglicle transmission driven by a 1959 Chevrolet engine for 5000'cycles, each cycle consisting of 6 seconds of open throttle operation followed by 6 seconds of closed throttle operation. At the beginning of each cycle, the transmission is engaged in a low setting and is allowed gradually to accelerate to 4100 rpm. at a torque of 370 foot-pound in -6 seconds. Theareafter the throttle is closed and the transmission is allowed to return to the original low setting. The operating conditions for the transmission and the engine are as follows:

Dynamic torque at shift 360-375 foot pound.

Governor cavity pressure (maximum) 12i1p.s.i. Governor cavity pressure (minimum) 1.5-2.5 p.s.i.

At the end of the test, the transmission is dismantled and inspected for (1) the condition of the clutch plate, (2) thrust Washer weight loss, and (3) plate wear. A

clutch plate shows no worse than light flaking and the plate wear is less than 0.08 inch.

The utility of thelub'ricating compositions of this invention as a crankcase lubricant in gasoline internal combustion automobile engines is shown by the results (summarized in Table V) of the modified version of the CRC- EX-3 test (the modification consisting in extending the test period from 96 hours to 144 hours). This test is recognized in the field as an important test by which lubricants can be evaluated for use under light-duty service conditions such as are encountered in the operation of passenger cars in urban traflic. In this test the lubricant is used'in the crankcase of a 19.54 6-.cylinder Chevrolet Powerglide engine operated for 144 hours under recurring cyclic conditions, each cycle consisting of: 2 hours at engine speed of 500 rpm. under 0 load, oil sump temperature of 100-125 F., and air fuel ratio of 10:1; 2 hours at-an engine speed of 2500 r.p.m.under a load of 40 brake horsepower,-oil sump temperature of 240-280 F and air: fuel ratio of 16:1. At the end of the test'the lubricant is rated in terms of (1) the extent of piston filling, (2) the'amount of sludge formed in the engine (rating scale of '80-0, '80 beingindicative of no-sludge and 0 being indicative of extremely heavy sludge), and (3) the total amount of engine deposits, i.e., sludge and varnish formed in the engine (rating scale of 100-0, 100 being indicativeof no deposit and 0 being indicative of extremely heavy deposit).

The eificacy of the lubricating compositions of this invention for use in a diesel engine operated under conditions of high speed and high temperature is shown by the results (summarized in Table VI) of a modified version of CRC-L-l Test (the modification consisting in the use of a fuel having a sulfur content of 1%, carrying out the test for 240 hours, and elimination of the replacement of the lubricant at the end of hours of testing). In this test the lubricating composition is used in the crankcase of a 4-stroke diesel engine having'a compression ratio of 15 to 1 operated under the following conditions: speed, 1000 r.p.m.; B.t.u. input per minute, 2900-3000; load, 20 brake horsepower; Water jacket outlet temperature,

F.; oil temperature, 140-150 F. The lubricating composition is evaluated according to (1) the piston j cleanliness (rating scale of 0-100, 100 being indicative of.

no deposit and 0 being indicative of heavy deposits) and (2) the amount of ring fillinga t i 1 1 Table VI Piston Cleanliness Test Sample Percent (Percent by Weight) Ring Filling What is claimed is:

1. A lubricating composition comprising a major proportion of a lubricating oil, from about 0.01% to about 2% by Weight of phosphorus as a phosphorothioate additive selected from the group consisting of oil-soluble Group II metal salts of phosphorodithioic acids having the structural formula RZO/ SH wherein R and R are substantially hydrocarbon radicals and contain at least about 7.6 aliphatic carbon atoms per atom of phosphorus and adducts of said metal salts with up to about 0.75 mole of an epoxide selected from the group consisting of alkylene oxides having up to about 6 carbon atoms in the alkylene radical, aryl-alkylene oxides having up to about 6 carbon atoms in the alkylene radical, chloro styrene oxides, epichlorohydrins, butyl 9,10- epoxy-stearate, epoxidized soyabean oil, epoxidized tung oil, and epoxidized copolymer of styrene with butadiene; and at least about 0.1% by weight, sufficient to reduce the corrosive tendency and to enhance the oxidation resistance of said lubricating composition due to the presence therein of said phosphorothioate additive, of anthranilic acid.

2. The lubricating composition of claim 1 characterized further in that the phosphorothioate additive is a zinc phosphorodithioate.

3. The lubricating composition of claim 1 characterized further in that phosphorothioate additive is a barium phosphorodithioate.

4. The lubricating composition of claim 1 characterized further in that the phosphorothioate additive is a zinc dialkylphosphorodithioate.

5. The lubricating composition of claim 1 characterized further in that phosphorothioate additive is a zinc dialkylphosphorodithioate in which each alkyl group contains from 3 to about 30 carbon atoms.

6. The lubricating composition of claim 1 characterized further in that the phosphorothioate additive is the adduct of an alkylene oxide having up to about 6 carbon atoms in the alkylene radical with a zinc phosphorodithioate.

7. The lubricating composition of claim 1 characterized further in that the phosphorothioate additive is the adduct of a zinc dialkylphosphorodithioate with a lower alkylene oxide having up to about 6 carbon atoms in the alkylene radical in a molar ratio within the range from about 1:0.25 to about 1:05 respectively.

8. A lubricating composition comprising a major proportion of a lubricating oil, from about 0.01% to about 2% of phosphorus as a zinc dialkylphosphorodithioate having at least about 7.6 carbon atoms in the alkyl radicals per atom of phosphorus, and from about 0.01% to about 1% by weight of anthranilic acid.

9. The lubricating composition of claim 8 characterized further in that the zinc dialkylphosphorodithioate is zinc dioctyl phosphorodithioate.

10. A lubricating composition comprising a major proportion of a lubricating oil, from about 0.01% to about 2% by weight of phosphorus as an adduct of a zinc dialkylphosphorodithioate having at least about 7.6 carbon atoms in the alkyl radicals per atom of phosphorus with up to about 0.75 mole of an alkylene oxide having up to about 6 carbon atoms in the alkylene radical, and from about 0.01% to about 1% by Weight of anthranilic acid.

11. The lubricating composition of claim 10 characterized further in that the alkylene oxide is propylene oxide.

12. The lubricating composition of claim 10 characterized further in that the relative molar ratio of the zinc dialkylphosphorodithioate to the alkylene oxide in the adduct is within the range from about 1:0.25 to about 1:05, respectively.

13. The lubricating composition of claim 10 characterized further in that the relative molar ratio of the zinc dialkylphosphorodithioate to the alkylene oxide in said adduct is about 1205 respectively.

14. The lubricating composition of claim 13 characterized further in that the zinc dialkylphosphorodithioate is zinc dioctylphosphorodithioate and the alkylene oxide is propylene oxide.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A LUBRICATING COMPOSITION COMPRISING A MAJOR PROPORTION OF A LUBICATING OIL, FROM ABOUT 0.01% TO ABOUT 2% BY WEIGHT OF PHOSPHORUS AS A PHOSPHOROTHIOATE ADDITIVE SELECTED FROM THE GROUP CONSISTING OF OIL-SOLUBLE GROUP II METAL SALTS OF PHOSPHORODITHIOC ACIDS HAVING THE STRUCTURAL FORMULA 